The AC compressor in my 76 Valiant is most likely seized up. It's the 2 cylinder style compressor. Aside from trying to find a working compressor, or retrofit it with an aftermarket unit which are really expensive, does anybody offer rebuild kits for these units?

"Rebuilt" units are still readily available from most any auto parts place or Radiator/AC shop. If your compressor is actually seized then it most likely has severe internal problems.

I also have a 1976 Valiant with AC. The freon mysteriously leaked out. It was in perfect working condition otherwise.